program Project2;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  x1, y1, x2, y2, x3, y3, i: integer;
  s: Real;
begin
  writeln('Enter the coordinates');
  readln(x1, y1);
  Readln(x2, y2);
  Readln(x3, y3);
  s:=Abs(x1*y2-x2*y1+x2*y3-x3*y2+x3*y1-x1*y3)/2;
  Writeln(s:0:3);
  Readln;
end.
